Massive keywords update, added configurable ansible_extra_special_keywords syntax group

[me-vlad]

• added almost all Ansible keywords
• removed deprecated 'only_if' keyword
• renamed ansible_with_keywords to ansible_loop_keywords
• added all loop keywords (loop, loopcontrol, until, retries, delay, with*) to the ansible_loop_keywords
• added optional ansible_extra_keywords_highlight_group variable to configure ansible_extra_special_keywords syntax group ansible_extra_keywords_highlight variable remained boolean for backward compatibility
• default systax group for ansible_extra_special_keywords changed to Structure (to differ from ansible_normal_keywords by default)

[pearofducks]

Really nice job, thanks for keeping backward compatibility and for putting this together!

[me-vlad]

Thanks @pearofducks , ansible-vim is very useful plugin for me